基于新型偏振稳定毫米波发生器的光载无线通信下行链路

为了降低ROF系统成本,增加传输距离,提高系统性能, 提出了一种基于新型偏振稳定毫米波发生器的光载无线通信下行链路传输系统.与传统ROF系统相比, 该系统利用保偏光纤光栅选频产生的两个偏振稳定激光信号拍频产生毫米波, 易于实现并降低了功率噪声对系统的影响.仿真分析了该系统中环形激光器强度、谱线宽度、保偏光纤光栅反射谱特性对毫米波性能的影响;分析了系统中保偏光纤光栅的群时延、长度、色散,双波长激光信号脉冲包络宽度、啁啾系数对毫米波频率的影响.优化保偏光纤参数, 差频产生60 GHz的毫米波信号,并分析该毫米波信号在ROF下行链路的传输性能,结果表明该毫米波 作为副载波调制到光波上从中心站传输80 km至基站后经天线发射至用户端,解调仍然得到很好的眼图, 充分证明了本方案的优越性能.     

抑光载波双边带Radio over Fiber双工通信系统设计

提出并模拟证明了基于两个电光相位调制器实现抑光载波双边带(Radio on Fiber,RoF) 双工传输系统设计方案.通过改变电光相位调制器的最大相偏量,实现了抑光载波双边带信号传输——使通信带宽加倍,而且很好地控制上下行传输信号的误码率.仿真模拟结果表明,发射功率为3 dBm的光信号在无放大、色散系数为20 ps/(nm·km)、衰减系数为0.25 dB/km的SMF-28单模光纤中传输时,其超高频RF调制信号的频率可达24 GHz,数据码元传输速率可达2.5 Gbit/s,传输距离40 km以上.     

基于光纤的光学频率传递研究

随着光钟研究的发展, 光钟的稳定度和不确定度均达到10^-18量级. 通过光纤可以实现光钟频率信号的高精度传输, 有望用于未来“秒”定义的复现. 演示了百公里级实验室光纤上的光学频率传递. 对于在实验室70 km光纤盘上实现的光频传递, 光纤相位噪声抑制在1-250 Hz傅里叶频率范围内均接近于光纤延时极限, 对应传输稳定度(Allan偏差)为秒级稳定度1.2×10^-15, 10000 s稳定度为1.4×10^-18. 实验室100 km光纤的光频传递秒级稳定度也达到了5×10^-15. 提出了光纤噪声用户端补偿的方案, 可以简化星形传递网络中心站的复杂度. 在25 km光纤上演示了该传递方案, 实现的传输稳定度接近传统前置补偿传递方案.     

抑光载波双边带Radio over Fiber双工通信系统设计

提出并模拟证明了基于两个电光相位调制器实现抑光载波双边带（Radioon Fiber,RoF）双工传输系统设计方案．通过改变电光相位调制器的最大相偏量,实现了抑光载波双边带信号传输——使通信带宽加倍,而且很好地控制上下行传输信号的误码率．仿真模拟结果表明,发射功率为3dBm的光信号在无放大、色散系数为20psj（nm·km）、衰减系数为0．25dB／km的SMF-28单模光纤中传输时,其超高频RF调制信号的频率可达24GHz,数据码元传输速率可达2．5Gbit／S,传输距离40km以上．     

基于偏振稳定双波长保偏光纤光栅激光器的可调谐微波/毫米波产生技术

首次提出了一种基于偏振稳定双波长保偏光纤光栅激光器的可调谐微波/毫米波产生技术, 利用保偏光纤光栅选频产生两个偏振稳定的激光信号, 采用扰偏器确保激光输出的两个正交偏振态功率的一致性, 最后输入高速光电探测器产生微波/毫米波. 通过对保偏光纤光栅施加不同大小的侧向应力, 可以灵活调谐输出的毫米波频率. 实验制作了基于偏振稳定双波长保偏光纤光栅激光器的可调 谐微波/毫米波产生装置, 通过对保偏光纤光栅施加不同的轴向拉力分别产生了20.407 和22.050 GHz的微波信号. 仿真产生了60 GHz的毫米波信号, 并分析该毫米波在光纤无线通信下行链路的传输性能, 结果表明该毫米波作为副载波调制到光波上从中心站传输80 km至基站后经天线发射至用户端, 解调后仍然得到很好的眼图, 充分证明了本方案的优越传输性能.     

基于开关键控调制的光载太赫兹正交相移键控信号产生

提出了一种基于开关键控（OOK）调制的光载太赫兹正交相移键控（QPSK）信号产生方案。基于双平行马赫-曾德尔调制器产生了一对光学八倍频边带信号,利用两个强度调制器分别将两路独立的OOK基带信号调制到八倍频边带的两个偏振态上,对两路偏振信号进行相位和幅度调整后再进行叠加,叠加后的光信号经过功率放大和光纤传输后在终端实现了光电转换,从而生成了太赫兹QPSK信号。在VPI仿真环境下,分别验证了80,240,400 GHz信号的传输性能。结果表明,生成的一个波特率为20 GBuad、频率为400 GHz的QPSK信号通过40 km的零色散位移光纤传输后,其误码率低于前向纠错码的阈值(3.8×10^-3)。该方案具有无需预编码技术和数模转换器的特点,降低了信号处理的复杂度和系统成本。     

基于综合光学调制技术的光纤无线双向通信系统设计

提出并研究了一种使用单光源的光纤无线双向传输系统.该系统只需在中心站配置一个可调谐激光器,以产生频率恒定的激光光源,通过综合光学调制（频率调制、强度调制）技术将基带信号调制到光载波上,最终形成60 GHz毫米波下行信号|同时,相同的光载波在基站被重用,作为上行链路传输光源.系统结合光载波重用技术和综合调制技术特点,合理利用资源,基站结构更为简化.仿真结果表明,该系统可以将速率达2.5 Gbit/s的数据在单模光纤中双向传输20 km,功率代价小于0.5 dB,相对已有的技术方案,该传输系统在传输功率、传输距离、传输性能方面具有明显优势.     

无滤波高倍频光载毫米波生成技术

提出了一种无滤波的高倍频光载毫米波生成方案.该方案未使用相关的光/电滤波器就可16倍频的毫米波信号.整个系统采用三平行的马赫-曾德尔调制器结构和单个马赫-曾德尔调制器级联,通过调整系统的参数可以很好地抑制所有冗余光边带,只留下高质量的8阶光边带,无需任何光/电滤波器就能够得到16倍频的高质量毫米波信号.另外,详细分析了系统的工作原理,并通过仿真验证了调制深度、消光比、移相器偏移以及调制器偏压对系统的影响.研究结果表明将2 Gbit/s的非归零码型数据与10 GHz的射频信号混频后作为马赫-曾德尔调制器的驱动信号,系统经过50 km光纤传输后的链路功率代价为1.0 dB,具有良好的传输性能.该方案对于无滤波的高倍频毫米波生成有一定的参考价值.     

基于MAX9259/MAX9260的CameraLink图像数据光纤传输技术

为了提高光电经纬仪上图像传输系统的性能,建立了光纤传输系统,本文针对传统Camera Link光纤传输系统方案中FPGA开发繁琐的问题,结合Camera Link接口协议和串行/解串行技术,设计了一种新的base型Camera Link的光纤传输系统,该系统采用Ser Des芯片组MAX9259/MAX9260代替编解码芯片,实现数据在Cameralink并行接口与光电转换模块串行接口之间的相互转化,并通过两种实验方案验证了系统的可行性。该方案省去传统方案中时分复用及异步FIFO缓存,降低了光纤传输系统的开发难度,并缩短了研发周期。实验结果表明:系统传输速率达到2. 5 Gb/s,具有传输稳定可靠,传输图像质量好,带宽高,抗电磁干扰能力强等特点,可满足多种像素时钟相机的需求。     

一种改进的双边带调制产生光毫米波的方案

提出了应用于光纤无线通信系统中一种改进的双边带调制产生光毫米波方案。在中心站采用强度调制将射频信号调制到光载波上产生一个双边带信号,滤掉中心载波后,利用光交叉复用器把双边带信号的上下边带模分开,将数据速率为2.5Gbit/s的基带信号调制到下边带模后,再与未调信号耦合后产生光毫米波,然后通过单模光纤传输至基站,在基站经过光电转换后产生电毫米波信号。从理论上对该毫米波的色散特性进行了分析,发现毫米波的接收功率不会周期的衰减。同时通过实验研究表明,下行链路信号通过光纤能传输50km而不需要色散补偿,功率代价小于1dBm。因此,该方法产生的光毫米波能有效克服光纤色散引起的信号时延而导致的基带信号退化,适合于远距离传输。     

A novel OCS millimeter-wave generation scheme with data carried only by one sideband and wavelength reuse for uplink connection

We propose a novel optical carrier suppression (OCS) millimeter-wave generation scheme with data carried only by one sideband using a dual-drive Mach–Zehnder modulator (MZM) in radio-over-fiber system, and the transmission performance is also investigated. As the signal is transmitted along the fiber, there is no time shifting of the codes caused by chromatic dispersion. Simulation results show that the eye diagram keeps open and clear even when the optical millimeter-waves are transmitted over 110 km and the power penalty is about 1.9 dB after fiber transmission distance of 60 km. Furthermore, due to the +1 order sideband carrying no data, a full duplex radio-over-fiber link based on wavelength reuse is also built to simplify the base station. The bidirectional 2.5 Gbit/s data is successfully transmitted over a 40 km standard single mode fiber with less than 0.8 dB power penalty in the simulation. Both theoretical analysis and simulation results show that our scheme is feasible and we can obtain a simple cost-efficient configuration and good performance over long-distance transmission.     

Optical millimeter-wave signal generation by frequency quadrupling using one dual-drive Mach–Zehnder modulator to overcome chromatic dispersion

We propose a novel approach to generate quadrupling-frequency optical millimeter-wave using a dual-drive Mach–Zehnder modulator (MZM) in radio-over-fiber system. By properly adjusting the phase difference in the two modulation arms of MZM, the direct current (DC) bias, the modulation index and the gain of base-band signal, the quadrupling-frequency optical millimeter-wave with signal only carried by one second-order sideband is generated. As the signal is transmitted along the fiber, there is no time shift of the codes caused by chromatic dispersion. Theoretical analysis and simulation results show that the eye diagram keeps open and clear even when the quadrupling-frequency optical millimeter-wave are transmitted over 110 km and the power penalty is about 0.45 dB after fiber transmission distance of 60 km. Furthermore, due to another second-order sideband carrying no signals, a full duplex radio-over-fiber link based on wavelength reuse is also built to simplify the base station. The bidirectional 2.5 Gbit/s data is successfully transmitted over 40 km standard single mode fiber with less than 0.6 dB power penalty in the simulation.     

Transmission Performance Improvement in Microwave/Millimeter-Wave Optical System Using Chirped Fiber Grating

A chirped fiber grating (CFG) written by the moving fiber/phase mask scanning beam technique with a uniform mask is used to demonstrate the dispersion compensation in the externally modulated microwave/millimeter-wave over fiber system. It is found that the use of the CFG is an efficient way to compensate for the severe RF power degradation induced by the fiber chromatic dispersion, which results in a significant improvement in the transmission performance. The signal to noise ratio is improved from 4.8 dB to 24.4 dB when 10.58 GHz RF signal carrying 5 Mbit/s QPSK format data is transmitted over 35 km single mode fiber.     

Absolute polar duty cycle division multiplexing over wavelength division multiplexing system

The performance of absolute polar duty cycle division multiplexing (AP-DCDM) over wavelength division multiplexing (WDM) system is presented based on the simulation results. The AP-DCDM signal has narrower bandwidth than conventional time division multiplexing (TDM) signal, which makes its implementation in WDM system advantageous. In this paper, characteristics of AP-DCDM and TDM signals in WDM system are compared at the speed of 40 Gbit/s per channel, for the minimum allowed channel spacing and the chromatic dispersion tolerance. The results clearly show that AP-DCDM performs significantly better than TDM. By using AP-DCDM, 1.28 Tbit/s (32 × 40 Gbit/s) was successfully transmitted over 320 km standard single mode fiber. Spectral efficiency of 0.64 b/s/Hz was achieved by using 10 Gbit/s transmitters and receivers without polarization multiplexing.     

机载光学整流罩与扫描反射镜尺寸及渐晕的设计分析

为满足机载光电系统的成像作用距离要求,对机载光学整流罩以及扫描反射镜的设计尺寸进行了理论仿真分析计算,并对研制的样机进行了试验研究。以实例形式给出了整流罩设计的作用距离与相关参量的计算结果,讨论了整流罩扫描系统的渐晕大小。装备该整流罩系统的样机,在近万米高空对音速某战机的红外长波扫描搜索距离可达到86 km,红外中波跟踪达到180 km,激光测距达到47 km。结果表明:根据探测作用距离理论模型分析计算,研制的机载光学整流罩及扫描反射镜光学系统达到了设计要求。     

一个新型的毫米波无线信号光纤传输系统及本振信号远程传送结构

摘要提出一个新型的毫米波光纤传输系统及本振信号远程传送的结构.此技术能为将来使用皮蜂窝网络提供宽带无线接入服务给出一个简单的基站接入点解决方案.计算和仿真结果表明,在激光器输出功率为－6.5 dBm,光放大增益为6 dB,激光线宽为1 MHz,75 MHz或150 MHz,误码率不超过10－9的情形下,622 Mbit/s的下行相移键控信号能够在传统单模光纤上传输超过30 km的距离.在具有相对大的激光器线宽150 MHz和光纤距离为30 km时,由激光器相位噪音和光纤色散所引起的（通过远程传送的）毫米波本振信号的额外相位误差的方差仅为1.74°.     

一种基于星座恢复的相干光OFDM系统非线性抑制方法

鉴于相干光正交频分复用系统（CO-OFDM）易受非线性效应影响,严重制约系统传输性能, 提出一种基于星座恢复的降低系统峰均值功率比（PAPR）的方法。对系统模型及作用机理进行分析,仿真结果显示,以10 Gbit/s的速率通过单模光纤传输720 km,基于星座恢复的CO-OFDM系统Q值较无非线性抑制的CO-OFDM系统有3 dB提高;另外,系统最佳限幅比例系数受色度色散影响,随着色散因子的增大,星座恢复效果也逐渐减弱,在传输240 km条件下,色散因子为12 ps/nmkm较6 ps/nmkm,限幅比例系数从0.9降低至0.8。     

Chaotic free-space laser communication over a turbulent channel

The dynamics of errors caused by atmospheric turbulence in a self-synchronizing chaos-based communication system that stably transmits information over an approximately 5 km free-space laser link is studied experimentally. Binary information is transmitted using a chaotic sequence of short-term pulses as a carrier. The information signal slightly shifts the chaotic time position of each pulse depending on the information bit. We report the results of an experimental analysis of the atmospheric turbulence in the channel and the impact of turbulence on the bit-error-rate performance of this chaos-based communication system.     

Optimization of pilot interval design in direct-detected optical OFDM system

The direct-detected optical OFDM (DDO-OFDM) system in frequency-selective fading fiber channel with three different types of pilot interval design has been experimentally investigated. In these schemes, the 2.28 Gbit/s QPSK-OFDM signal is transmitted over 100 km fiber in the system. The experiment results show the scheme with sparse pilot as frequency increasing shows the best performance for DDO-OFDM system.